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Trilostane/Vetoryl Information and Resources

Trilostane is the chemical name for a medication that effectively treats Canine Cushing's Disease. Worldwide, the only licensed veterinary version of trilostane is manufactured in the U.K. by the Dechra Group under the brand name of "Vetoryl." Vetoryl received FDA approval for sale in the U.S. beginning in 2009. Vetoryl is generally marketed in four dosage strengths: 10 mg., 30 mg., 60 mg., and 120 mg. capsules. In the U.S., 5 mg. capsules are also available.

All dosage strengths of brand name Vetoryl capsules are now sold in the U.S. by veterinarians and also via internet pharmacies. Additionally, several pharmacies in the U.S. are compounding and selling their own versions of trilostane for veterinary use. For members who obtain compounded trilostane, we encourage you to contact your pharmacy directly regarding the ongoing availability of specific dosage strengths.

Dechra's Recommendations Regarding Treatment and Monitoring

Dechra provides published information about Vetoryl as well as guidelines for its use. For U.S. pet owners, here are links to some especially helpful resources on Dechra's U.S. website, including direct contact information in the event that you or your vet have questions. Additionally, for all our owners worldwide, please take note that as of 2018, a new treatment monitoring protocol has been introduced by Dechra U.K./E.U. Please scroll down to find a posting re: this new, “Pre-pill” Vetoryl (trilostane) testing protocol.

Here is a link to Dechra's international homepage. Once there, you can click on information that is specific to your own country or part of the world. In order to convert laboratory values from international charts and literature (nmol/l) into U.S. lab units (ug/dl), divide the values reported on the international charts by 27.59.

New, Lower Trilostane Dosing Recommendations (2015)

During the past decade since Vetoryl (trilostane) was first introduced as a Cushing’s treatment, recommendations re: the size of the initial starting dose have lowered. This revision is based on accumulated worldwide research and clinical experience, and reflects the current thinking of the majority of the specialists treating Cushing's here in the U.S. as well as elsewhere. It also reflects experiences we have seen here on our forum during this past decade. Put simply, dogs seem to experience fewer unwanted side effects when they are started at lower doses and adjusted upwards if need be, rather than vice versa.

Dechra (manufacturer of brandname Vetoryl) has a worldwide presence including a U.S. office. However, Vetoryl is made in the U.K. and to be legally sold there, Vetoryl must be properly registered with their "VMD" (Veterinary Medicines Directorate). To be legally sold in the U.S., Vetoryl is regulated by the FDA. Both regulatory bodies require their own specific filings and published literature re: medication. Until recently, the published initial dosing recommendations for Vetoryl were similar in both countries. However, in 2015 the official "Summary of Product Characteristics" for Vetoryl filed in the U.K. was revised to reflect this new initial dosing recommendation:

The starting dose for treatment is approximately 2 mg/kg, [or approx. 1 mg/lb] based on available combinations of capsule sizes.

This recommendation can be found here (just enter "Vetoryl" in the "Search" window, then click on the SPC for any dosage strength):

We believe it is unfortunate, but neither the U.K. Datasheets nor the U.S. Product Inserts that are actually packaged within boxes of Vetoryl yet reflect simplified dosing language identical to Dechra's revised "SPC." In the U.S., the original 1-3 mg/lb dosage range dating from 2009 remains published on the FDA-approved insert. However, please note that the range is immediately followed by this newer sentence added to the 2014 revision of the insert, "Start with the lowest possible dose based on body weight and available combinations of capsule sizes." So in truth, this is the same recommendation as that of the new SPC revision: start as closely as possible to the 1 mg/lb formula.

For any vet who has questions about the appropriateness of starting with a lower rather than a higher dose, we encourage the vet to call Dechra directly in order to discuss whether there are individual factors that make a higher dose more desirable for any given dog. However, to reinforce the general desirability of lower initial starting doses, here are quotes from several noted U.S. endocrinology specialists. Please note that 2.2 mg/kg translates into 1 mg/lb.

Dr. David Bruyette (2016):

Also, it is my recommendation when using the manufactured product [Vetoryl] to ignore the dosage recommended on the label, as it is too high. In fact, the manufacturer is in the process of trying to get the label dosage revised. I recommend a starting dosage of 1 to 2 mg/kg [.5 to 1 mg/lb] once a day in the morning with food.

New, “Pre-pill” Trilostane monitoring protocol (2018)

Those of us living in the U.S. have recently learned of a new Vetoryl (trilostane) monitoring protocol that is being used successfully in the U.K. and Europe. Historically, ACTH stimulation tests had been recommended for trilostane monitoring purposes worldwide, and the ACTH remains the “gold standard” for monitoring Lysodren (mitotane) treatment. However, due to the different manner by which trilostane alters adrenal response, researchers have questioned whether its therapeutic effect might be better assessed in a different way.

The new monitoring protocol involves a much simpler test: measuring a dog’s resting cortisol level right before the administration of the next dose (“Pre-pill trilostane testing”). Very importantly, the resting cortisol level is evaluated in conjunction with the dog’s appearance and symptoms. Unresolved symptoms may trigger a dosage increase as long as the pre-pill cortisol has not dropped too low. However, any time a dog exhibits problems consistent with low cortisol, an ACTH test remains warranted.

One big advantage to owners is financial: a resting cortisol is much less expensive than an ACTH stimulation test. Therapeutically, the advantage is that it may be easier to identify the trilostane dose that will adequately relieve symptoms. Dechra (manufacturer of Vetoryl) has issued a new monitoring flowchart that is being distributed and used by vets in the U.K. and E.U. We are including it below. In addition, we have added links to some of the relevant research summaries.

Unfortunately, this new protocol is not yet being offered or discussed by Dechra U.S.A. because the product labeling formally approved here by the FDA only addresses ACTH testing. Over time, that product info may change. However, in the meantime, we encourage interested U.S. (and Canadian) owners to print out the European flowchart to show their vets. In turn, general practice vets should consult with internal medicine specialists about this new protocol. It’s our understanding that all specialists in this country have now been notified about the new protocol, and hopefully they will be able to advise GP vets re: its proper use. Due to the heavy reliance upon observed symptom resolution or ill effects, owners will also play a critical role in this new monitoring protocol.

Here are related research summaries. You will see that resting cortisol levels taken pre-pill, three hours post-pill, and post-ACTH stimulation have all been compared. The current conclusion is that if only a single value is relied upon for dosing decisions, the pre-pill resting value is the most useful.

Compounded Trilostane in the U.S.

A decision regarding using a compounded version of trilostane is one that you must make in conjunction with your vet. Be aware that compounded versions of trilostane, while in widespread use, are not the equivalent of generics, and do not carry the same U.K./U.S. certifications as does Vetoryl. There are several pharmacies in the U.S. that are compounding and selling their own versions of trilostane for veterinary use. However, the FDA, various compounding pharmacies, and other interested parties are currently involved in ongoing discussion seeking to define the regulatory oversight associated with both human and veterinary compounding.

For more information regarding the use of compounded medications in the U.S., here is a recently revised brochure published by the American Veterinary Medical Association (AVMA). One section of particular interest is "Questions to Ask Your Pharmacist" in the event that a compounded drug is prescribed for your pet.

Included in the "Veterinary Compounding" brochure is the following explanation as to the difference between compounded and generic drugs:

Generic drug products are very different from compounded preparations. Generic drug products are FDA-approved, which requires a demonstration of bioequivalence of safety and efficacy with the pioneer drug product. Generic animal drug products are identified by an Abbreviated New Animal Drug Application (ANADA) number on their label or in FDA drug references. In contrast to generic drugs, compounded preparations lack FDA approval.

Additionally, here is the first of a series of articles that discuss current legal and regulatory issues associated with veterinary compounding in the U.S. All subsequent articles can be accessed from Part 1.

Disclaimer -- The content on this site is provided for informational and educational purposes only. While we make every effort to present information that is accurate and reliable, the views expressed here are not meant to be a substitute for the advice provided by a licensed veterinarian. Please consult with your veterinarian for specific advice concerning the medical condition or treatment of your pet and before administering any medication or pursuing any course of treatment that you may read about on this site.

The views and opinions expressed by contributors to this forum are strictly their own and do not necessarily reflect the opinions and views of the owners, administrators, or moderators of this forum and the k9cushings.com website.